The purpose of this Phase II study is to test how well A-100, a man made form of a naturally occuring hormone called Leptin, works in controlling blood sugar levels in overweight people with type 2 diabetes and to determine how safe the drug is compared to a placebo. Leptin is made in fat cells and is believed to be involved in controlling blood sugar and body weight. A-100 may work by increasing the body's response to insulin and it may cause some weight loss. Both results would be expected to give patients better blood sugar control.